The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.
Nutrients are essential in the growth and development of crops. Crops absorb nutrients such as nitrogen, phosphorus, and potassium in the surrounding soil to facilitate crop growth. Different types of crops have different requirements for each nutrient. When a crop is unable to meet its nutrient needs, the crop suffers. For example, a lack of nitrogen may lead to destruction of a crop's leaves. Additionally, once the nitrogen concentration in a plant decreases below a critical threshold, photosynthesis and dry matter accumulation is negatively impacted. An end result is that the yield of a crop which does not receive enough nutrients is decreased.
While nutrients in the soil are important to plant growth, it is difficult to determine when soil lacks one or more nutrients without performing nutrient tests. Additionally, the impact of a specific nutrient application is not readily apparent. For example, an application of forty pounds per acre of nitrogen at one time may result in a net increase of ten pounds of nitrogen per acre available to a crop due to nitrogen loss through a variety of factors and low transmission rates to the crop. The same application of forty pounds per acre of nitrogen at another time may result in the majority of the applied nitrogen being available to a crop. Without an understanding of all of the factors that affect whether a crop will receive the nitrogen added to a field, nitrogen application tends to be relatively blind. A farmer may apply nitrogen to a field at specific stages in a crop's development or when the crop appears to be suffering from a lack of nitrogen. Such applications of nitrogen are inefficient as they either involve wasting nitrogen or not adding enough nitrogen to satisfy the needs of a plant. Additionally, nitrogen lost to the field through leaching may create environmental problems when the nitrogen joins the watershed.
To identify nutrient content values in soil, a computer system may run a nutrient content model which takes in specific input values, such as temperature, soil type, crop type, and precipitation, and transforms the values to identify a nutrient content in the soil at various different points. While a nutrient content model is useful for generally identifying how much of a particular nutrient is in the soil, nutrient content models are not foolproof. Nutrient content models are subject to various sources of errors, such as errors in the input data, errors in universal parameters, and errors based on physical processes which are not being modeled.
A second method of identifying nutrient content values in soil is to measure the nutrient content in the soil using techniques such as near infrared reflectance spectroscopy on core samples removed from the field. Measurements of nutrient content in soil can be extremely accurate for the source of the soil sample. A problem with basing farming practices on measurements of nutrient practices is that a farmer would have to constantly be measuring the nutrient contents in a large number of locations.
Often, soil measurements are taken from a field at limited points in time. For example, farmers often take a measurement of nutrient content prior to side dressing in various locations across the field. Thus, as there are often limitations to the number of nutrient content measurement values received for a particular field, there is a need for a system which increases the accuracy in estimating nutrient content in soil using only a limited number of samples of nutrient content in the soil.